Separating or cutting units for severing a yarn of a fully wound bobbin in a ring spinning machine are described in the patent literature. A ring spinning bobbin, it will be understood, is usually a bobbin built upon a core or sleeve which is mounted on a spindle. The roving may be drawn from roving bobbins through drafting frames of the ring spinning machine and pass through a thread-guide eye above the spindle and then through a traveller orbiting the spindle on a traveller ring. The traveller ring can be raised and lowered with respect to the bobbin on a ring rail while the spindle is provided on a spindle rail which generally also can be raised or lowered, e.g. for the bobbin change operation. The spindle can be provided on the spindle rail with a whorl tangentially engaged by a belt for driving the spindle and below the sleeve on the spindle a thread reserve can be collected to hold the yarn preparatory to severing it for bobbin removal or preparatory to the winding of the yarn on a freshly positioned core or sleeve. Generally above this reserve, a cutting device can be provided for the purposes described. Mention may be made, for example, of German Patent Document DE 42 37 475 A1 and German Patent Document DE 40 15 707 C2. The cutting system described in these references have the tooth arrangement and the blade arrangement formed on two separate parts which can be injection molded or pressed or stamped elements. Of course this means that two A separate parts for each spindle or station of each ring spinning machine must be provided and assembled together and mounted on the spindle. When it is recognized that ring spinning machines may have very large numbers of such spindles and stations, it will be apparent that the cost of such systems is substantial. Furthermore, since the blades constitute wear parts, they must be replaced and the replacement cost, even through occasional, can be considerable as well. Mention may also be made of the fact that when the toothed member and the blade member are fabricated separately and assembled together, spaces inevitably are formed in which the thread or yarn can catch. These may have to be manually cleared.
Reference may also be had to German Patent Document DE 43 36 359.8 (see also U.S. Pat. No. 5,562,268) which provides still another type of cutting blade which has the advantage of being fabricated more inexpensively than more complex blades but which nevertheless must be used together with a toothed member if it is to be fully effective. German Patent Document DE 32 02 888 A1 describes a ring spinning machine with a device for automatically removing the bobbins and, in conjunction therewith, cutting the thread and located above the thread reserve portion on the spindle. Here the blade itself is notched but no separate toothed member is provided nor are there toothed 156 formations which serve to protect against injury by contact with the cutting edges. Finally, mention may be made of the German Patent Document 24 61 623 C2 which also discloses a notched blade which is not used in conjunction with protective teeth or like members.